How sensitive is climate to perturbations? This is a central scientific uncertainty in projecting human-induced climate change over the next century and beyond. State-of-the-art coupled ocean-atmosphere-land models predict that under 'business as usual' emission scenarios, global mean surface temperatures in the 2090s will be 2.4-6.4 K higher than the 1980-1999 average, with much greater warming in the Arctic.

Uncertainties in climate feedbacks, including clouds, water vapor, snow and ice albedo, and in ocean heat uptake efficiency lead to the large range in the predictions. There is even more scientific uncertainty in biospheric and ice sheet feedbacks, which are of primary importance for climate changes of the past,
and are also important to longer-term predictions of the future. This year's Summer Institute focused on feedbacks in all parts of the Earth system which affect the global climate.